Filtering carafes including a system of determination of the conditions of exhaustion of a filtering cartridge are familiar, for example by U.S. Pat. No. 5,900,138 of the same applicant.
In filtering carafes the problem of pointing out to the user the need to replace the cartridge once it is exhausted is very common. Typically, exhaustion of the cartridge is monitored through the use of two parameters, the number of filtering cycles carried out from initial activation and/or the amount of time from said activation. It is clear that the filtering material contained in the cartridge progressively loses its capacity of purifying water through use and time.
Even if these two factors represent efficient parameters in order to evaluate the conditions of efficiency of the filtering cartridge, the indication based on these factors only may turn out to be unsatisfactory. There is in fact a third important factor for calculation of the lifespan of the cartridge: the quality of the water to be filtered and the concentration of pollutants that it contains.
The filtering power of the cartridge does not vary according to the quantity of water treated but also according to its quality.
The filtering carafes available up until today include a counting system of the filtering cycles carried out from initial activation of the cartridge, identified for example according to the counting of the number of accesses to the first water collection basin to be filtered. In some cases there is also an auxiliary counting system which counts the amount of time from the initial activation of the cartridge, compared with a time limit of lifespan of the cartridge, in order to calculate the exhaustion of the cartridge according to the first of the two events (exhaustion of time from the first activation—counting of the filtered water) that is verified.
Carafes capable of calculating the exhaustion of the cartridge according to the quality of the water treated are not currently known.